At Sturgis last year, I saw a kid ride in with his mom(i am guessing) must have been 8-10 yr old. It was a adventure cross type bike like a Multistrada or something to that nature, but he was strapped to her in a harness pack too.
My wife used to ride with her dad on a full bagger Harley ElectraGlide and said she would fall asleep. But was safe due to the full seat and trunk that had kind of a built in arm rest feature. So I could see if it was just a tool around the neighborhood, or down to the next town that the lessor of two evils to you would probably be the harness. Or Barrow/rent a full seated cruizer, two wheels is two wheels. ALthough two Italian wheels are tops-of-food chain!
My oldest is two, and I don't know what I am gonna do when the time comes for him